Public and private networks, which can based on standard or proprietary protocols, operate for a given set of users that subscribe to the network. Users and network operators are required to acquire, either by purchase or lease, specialized equipment such as communication nodes and subscriber units to operate in these various networks. Communication nodes include base stations and access points that transmit signals to and receive signals from subscriber units so that the subscriber units can communication with one another as well as other communication nodes. The communication nodes can also provide access to other networks from which the subscriber units can be provided signals.
The networks that use this various equipment can include wide area networks (WANs) and local area networks (LANs), including wireless LANs (WLANs,) that each operate according to the different protocols. These different protocols can include Global System of Mobile Communication (GSM), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), CDMA2000, Wideband CDMA (W-CDMA) and Universal Mobile Telecommunication System (UMTS), Orthogonal Frequency Division Multiplex (OFDM) as well as protocols that abide by IEEE 802.xx standards, such as IEEE 802.16.
As the networks improve, it becomes more and more necessary for a network that uses one protocol to be able to provide access to devices that operate according to a different protocol. In such a situation, a network operator installs various communication nodes as a part of the network infrastructure. These communication nodes provide network access using a first protocol and provide access to subscriber units that operate using that first protocol. In order to improve service and to take advantage of the developments provided in new technologies, network operators may upgrade communication nodes that operate using different protocols than those originally provided. It is also possible for the network operators to install new communication nodes using the new protocol that operate along side the communication nodes that use the old protocol. The network users, however, may still be using equipment that operate using the old protocol and may not be willing or able to replace the subscriber units to therefore easily operate using the new communication nodes. Nonetheless, the users may want to be able to take advantage of some of the new features and capabilities of provided by the new protocol. Thus, new communication nodes need to be backwards compatible with older equipment.
In addition, technical innovations as seen in the progression of new protocols introduce issues that may not always be backward compatible such that a device that operates according to a first protocol may no longer be able to work on the network where the protocol has been modified into a second protocol. This is also true with respect to different aspects of the protocol including medium access. Replacement of older systems with new systems that require new communication nodes can be associated with service disruptions, time delays and other costs.
Continued development of OFDM technology for wireless access raises the prospects of wide availability of low-cost subscriber units that are capable of operating in the same frequency range as subscriber units that operate on other networks such as Canopy systems, which is provided by Motorola, Inc. of Schaumburg, Ill. There is a need to offer access and to provide connectivity to a mixed population of subscriber units that use one protocol and subscriber units that use another protocol based on OFDM technology.
In view of the foregoing, there is a need to address the issues raised by a subscriber unit roaming into a cell that is services by a communication node where the subscriber unit uses a protocol similar to but not completely compatible with the protocol used by the communication node. It is also possible for a low cost subscriber unit that will close the gap between the linear and frequency modulation radios that need to be backwards compatible with networks. It may not be possible, however, to provide services for these users that require backward compatibility by reserving channels for the very low-traffic-density populations of subscriber units because it will utilize available spectrum capacity that would be better utilized by the new protocols. In addition, issues exist when transitioning between the new and old protocols relating to the service disruptions, delays and costs. Accordingly, there is a need to provide a time multiplexing of communication system that deploy distinct interfaces and protocols while sharing the same physical communication medium. There is also a need to provide multi-protocol communication nodes capable of communicating with devices that support different air interfaces and protocols.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.